I don't think it's your VPN (I have one too that disconnects every time as well). I think Blackberry World has flagged your account as a "risk" and will not let you purchase/open a BlackBerry World account

You'll have to contact BlackBerry and have them try and fix it. It'll take awhile..sorry.

Thanks for responding
I'm living in Iran so I have to use vpn and of course can't call BlackBerry!! I think this issue is because of my simcard,is payment options related to simcard? Can someone check?
I appreciate it.